Modern Mining February 2020

expenditure and a reduction in estimated operating costs, eliminating the need for multi-stage crushing and screening of rock ahead of milling. Overall capex for the processing plant has been reduced by approximately AU$15-million (about US$1-million) from the total plant capital, originally estimated at AU$109-million (US$72,8-million) and the plant unit operating costs reduced by 5% from a base estimate of AU$16,1 (US$10,75) per tonne. This represents a significant improvement to be incorpo- rated into the optimised and updated BFS Report, due for completion in early Q2 2020. “We are very pleased that we can now begin to lock in the anticipated project optimisations with associated positive capex and opex savings. The plant optimisation studies progressed alongside studies on improved water treatment and optimi- sation of our mine-to-market schedule, all of which are now nearing completion. The successful metal- lurgical optimisation of the process flowsheet has culminated in securing the right to purchase two new mills which are available at a significant dis- count to mills which would otherwise have to be placed on order as a long-lead item. These optimi- sations all promise to deliver an uplift on the already excellent investment case for the Prieska project,” concludes Smart. 

continent, both in terms of operational efficiency and the approach to skills transfer and harmonious relations with communities. Their involvement in developing Prieska will be invaluable.” Project optimisations Meanwhile, following the successful conclusion of value engineering studies on the ore processing plant design and layouts for the Prieska project, Orion Minerals has moved to secure specific mills required to realise the identified improvements via an option agreement. The company has identified two new 3 600 kW mills that are immediately available at a significant discount to similar mills, which would only be avail- able from manufacturers with long lead times. Securing the mills facilitates the incorporation of SAG milling into the ore processing flowsheet, in place of the ball milling arrangement selected in the Prieska project Bankable Feasibility Study (BFS). The revised ball and SAG milling configuration will allow significant operational flexibility and facili- tate processing of Prieska ore at a rate of up to 20% above design throughput, allowing capacity for future expansion. The use of SAG milling simplifies plant layout and operation, with significantly reduced upfront capital

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